The present invention relates to telecom network media overload. More particularly, and not by way of limitation, the present invention is directed to a system and method for controlling signaling overload.
Prior Art and Problems
In Next Generation Networks (NGNs), many protocols, e.g., H.248.11 (also known as Gateway Control Protocol) are used for controlling media setup of a call. The protocol messages are processed on a central processing unit (CPU) of corresponding nodes.
Different types of nodes have different signal processing capacity and some nodes might have significantly higher capacity than others. Because of that there are scenarios, where signaling overload caused by the source node in a specified target node has a high probability of occurring.
Signaling overload causes system performance degradation even if the node is able to protect itself by rejecting offers. External overload control mechanisms have been developed to restrict in advance (in a source node) the traffic that is offered to a target node. There are call-gapping algorithms that decide whether the offer should be sent out to the target. If the desired maximal offer characteristics are known (determined as part of the external overload control) decision logic in the source node is referred as a throttle.
An external overload control mechanism itself can control different types of descriptors of traffic flows in a system. For example, Windows-based solutions control the message turnaround time with a throttle limiting the number of offers in the system while other solutions work with restricting a percentage of the offers compared to the previous period of time. Many others like H.248.11, control the rate of the offers and use token bucket as a throttle.
FIG. 1 depicts external overload control architecture. Typical requirements on an offer rate limiting throttle in H.248.11 are: [a] the rate of the offers sent out should be limited according to the rate determined by other parts of the external overload control; [b] an offer should always be sent out once the limit is not violated; [c] when only one offer can be sent out and there are two candidates, always send out the one with the higher priority; and [d] once different traffic classes are defined (on the same priority level), and there are candidates not to be sent out because of the limitations then the offer rate representing the resource should be split according to some defined agreements between the traffic classes (Service Level Agreements). (req-3)
The problem with these requirements is that once they are put into a real system environment it is very hard to decide whether they are being met or not. Furthermore, the requirements might have a different interpretation and even concurring exact definitions when all of them can not be satisfied at the same time.
The rate of offers is not violated on average and according to the watermark level the maximal peak in traffic; thus, the maximal violation of the rate is also limited. Setting of a watermark parameter determines how likely the bucket produces higher throughput rates for short times (violates [a]) or does not send out candidates although there would not be rate violation (violates [b]).
The rate does handle priorities by applying different watermarks for different priority levels. Thus, throughput characteristics are different for priorities; i.e., calls with higher priority cause higher peaks in traffic (requirement [2] ok).
Does not handle traffic classification so can not handle throughput share type of Service Level Agreement (violates requirement [d])
There are methods like Weighted Fair Queuing that queues offers and thus causes delay in the transmission which solves [d]. It is often required to give a solution without using queues but providing maximal throughput.
“Rate Based Call Gapping” is a method based on offer rate and admission rate measuring that provides a solution for all three requirements without applying queues but its priority handling is not straightforward.
This means that if the parameters are set so that they affect the priority handling then the behavior still depends on incoming traffic and there is always a positive probability of a lower priority call being admitted because of throughput share SLA priority and a higher priority call may be admitted although the admittance violates SLA agreements.
It would be advantageous to have a system and method for resource sharing without buffering requests that overcomes the disadvantages of the prior art. The present invention provides such a system and method.